Quite a lot of folks thought he sounded like a good fit, but he greatly disappointed people. Meg Bussert was good as Marian (I've nearly always seen good Marians in various "Music Man" productions I've seen over the years), but Van Dyke's song-and-dance man energies failed him; the original show was first offered to folks like Gene Kelly, Danny Kaye, Dan Dailey, etc. before Robert Preston surprised everyone with his great performance. Another reason Preston succeeded is that Harold Hill is essentially a character role, and Preston had been playing villains in lots of Hollywood westerns, among other roles in films and Broadway prior to playing Harold Hill. Hill is supposed to have some sex appeal, but he's at heart playing a character -- lest we forget, Marcellus first calls him "Greg" upon seeing him in Iowa, so Harold Hill is a new persona. I think Van Dyke could have pulled it off. He wasn't all "niceness". I recall seeing him play an alcoholic in some tv movie where he made himself not very likable, but apparently that was kind of what was going on in his real life off-stage while doing the "Music Man" in NYC and what apparently sapped his energy on stage. I was very happy to see him dancing recently and energetically in the recent "Mary Poppins Returns" as a nonagenarian.